Seismic Assessment
Prior to the Kaikoura earthquake on 14 November 2016, the Rotorua Museum team had already commenced a seismic assessment of the building as part of Building Act requirements. Post the 7.8 magnitude Kaikoura earthquake GDC Consultants Limited completed a Rapid Seismic Assessment (RSA), following the discovery of additional cracks in the building. As a result of the RSA, the Museum was closed two days later.
Detailed Seismic Assessment
GDC Consultants Limited were commissioned by Rotorua Lakes Council (RLC) to undertake a Detailed Seismic Assessment (DSA) of the Rotorua Bath House building in which Rotorua Museum is housed.
Following their extensive investigations the building was rated at 19% of New Building Standard (NBS), meaning the building is considered earthquake prone.
The building has had a number of different uses throughout its history. Prior to its closure the building was home to Rotorua Museum and was hosting around 130,000 visitors each year.
Because of it high level of public use, it has an Importance Level 3 (IL3) building classification. This means that in the event of a failure there is considered to be high consequence for loss of human life, or very great economic, social or environmental impact.
Assessed Seismic Ratings
The Detailed Seismic Assessment rated the building at 19% NBS (IL3). The rating is applied to the whole building, but is governed from the lowest rating of 19% NBS (IL3) in the intermediate south wing.
In isolation, the original Bath House and new north wing are rated at 27% NBS (IL3) and the new south wing is rated at 74% NBS (IL3).
The low 27% rating for the new North Wing Extension is governed by the low rating in the adjacent northern wing.
The Bath House is classified as a Grade E building, and represents a relative risk to occupants 25 times greater than expected for a new building, indicating a very high exposure to risk.
A building with a seismic rating less than 34% NBS is considered to be an Earthquake Prone Building. A building rating less than 67% NBS is considered to be an Earthquake Risk Building.
With a rating of just 19% NBS (IL3) the Museum building is therefore categorised as Earthquake Prone.
